The present invention relates to stringing of electrical conductor or cable on power transmission towers and more particularly to a novel device for fixing a datum on adjacent cables in order to determine if the cables have subsequently shifted along their longitudinal axes one relative to another.
The "stringing" of electrical conductor generally proceeds along the following pattern. Transmission towers having laterally extending cross-arms, for supporting electrical conductor, are erected at spaced-apart locations along a predetermined ground path. Suspended from the laterally extending cross-arms are insulators which are provided for supporting the electrical conductor. For purposes of illustration, it is assumed that three side-by-side positioned electrical conductors are to be strung between insulators on adjacent towers. Initially, travelers are mounted on the bottom of each insulator, the travelers including three grooved pulleys for accommodating or training the electrical conductors.
To facilitate stringing, the use of helicopters has been found to be particularly advantageous. For instance, one end of a cable or line from a spool may be connected to a helicopter. The craft then lifts off and transports the line, as it is payed out from the spool, for connection to the travelers on the transmission towers. Because electrical conductor is quite heavy, it may not be readily payed out from a spool by means of a helicopter. Rather, a so-called "sockline," which is wire rope of substantially less weight, is initially connected to the helicopter. The helicopter then flies alongside the predetermined path, pays out the sockline from the spool and places it in the center wheel of each of the travelers. After the sockline is placed in the last traveler, the line is released and attached to the end of another wire rope or ropes known as "hardlines." The sockline spool is mounted on a power-driven drum or winch and such is actuated to pull the sockline and hardlines back toward the first transmission tower.
When the hardlines reach the first tower, each hardline is connected to electrical conductor and the hardlines, joined with the electrical conductors, are then pulled back toward the end transmission tower. The result is the stringing of the electrical conductor which is now supported in the travelers. Dependent upon the spacing between adjacent transmission towers, the terrain, and local wind factors, it has been predetermined to what extent the electrical conductor between adjacent towers should "sag." Each electrical conductor must sag with a certain predetermined catenary curve, and suitable surveying techniques are used in conjunction with sagging or tightening the electrical conductor to set such catenary curves.
Next, it is necessary to mount permanent shoes at the bottom of each insulator so that the electrical conductor may be transferred from the moveable travelers for permanent mounting in the shoes. However, there may be a time lag between transfer of the electrical conductor from a traveler to a shoe. During this time lag, temperature changes, wind effects, and other factors may alter the catenary curve of each of the electrical conductors. Stated differently, the electrical conductors may shift along their longitudinal axes, one relative to another. Accordingly, it is common practice to "mark" each of the electrical conductors adjacent a traveler immediately after setting the catenary curves between adjacent transmission towers.
Typically, a workman is positioned above the insulator and utilizes a long pole having ink or other marking material provided on one end thereof to mark the electrical conductors. The workman marks each of the conductors along what is hoped to be a common line. Thus, if changes in the relative positions of the electrical conductor occur, such will be perceived when the electrical conductor is mounted in a shoe because the previously provided marks will not lie on the common line. Accordingly, the electrical conductors are then suitably shifted so that the marks appear to lie on the common line.
Considering the above-described marking procedure, which is exemplary of the prior art, it should be apparent that there are several significant disadvantages. First of all, a mark created by ink, crayon, etc. is subject to removal or obfuscation by the weather. In addition, the workman charged with the task of marking uses substantial guesswork in creating the marks along a common line. The workman can only hope that a series of say, three marks, one provided on each conductor, are scribed along a common line which is generally perpendicular to the longitudinal axes of the electrical conductors. Considering the outcome of this guesswork, it should be appreciated that if the marks are not accurately aligned along a common reference or datum and are offset, even as small an amount as 1/2", the result will be wide deviations in resetting the catenary curves from those curves originally set.
Still another problem with the prior art marking of electrical conductor resides in the fact that the marks may not be readily perceived. For instance, it may be necessary for an observer on the ground to view the marks. If marking is provided on top of the electrical conductor, it is virtually impossible for a ground observer to see same. This is especially true in view of the fact that transmission towers may reach substantial heights with the laterally extending cross-arms being located 75 feet above the ground or higher.
Accordingly, it is an object of the present invention to provide a novel marking device for providing a datum on a plurality of objects, such as spaced-apart conductors or cables having their longitudinal axes lying generally parallel to one another which includes a dispenser means for releasably holding a plurality of attachments. The dispenser means is shiftable, by means of a workman, relative to the cables, for effecting cable-attachment contact which results in substantially simultaneous release and coupling of an attachment onto each of the cables.
It is another object of the present invention to provide a dispenser means, as described above, which includes a novel mounting for supporting the attachments in an aligned manner along a common reference so that when the attachments are released, after contacting the cables, they will be substantially aligned on the common reference. This reference then provides a datum on the cables. This is necessary for accuracy when the cables are later readjusted so that the attachments are aligned.
Still another object of the present invention is to provide a novel type of attachment which is formed as a resilient annular band. Each band is elastically deformable radially outwardly so that it is initially loaded on the dispenser means in a "sprung" orientation. When a cable contacts an inside surface of the band, the band is released from the dispenser means, deforms radially inwardly, and contracts to grip the cable along a circumferential portion thereof. The band (which may be brightly colored) is thereby "clipped" onto a cable and is readily visually perceivable by a ground observer.
Yet another object of the present invention is to provide an orienting means connected to the dispenser means for positioning the attachments so that the common reference will be substantially perpendicular to the longitudinal axes of the cables. Thus, when the attachments or bands are "clipped" onto the cables, they will be clipped along the common reference which, in turn, will be perpendicular to the longitudinal axes of the cables. Accordingly, if a change in the relative positions of the cables occurs, the cables may be repositioned so that the bands are aligned along the common reference.
These and additional objects and advantages of the present invention will be more readily understood after a consideration of the drawings and the following detailed description of the preferred embodiment.